Higher vehicles are charged at a higher toll rate because they are assumed to be heavier , thus more wear on the road. With the lack of fuel tax increases which funds the State & Fed DOTs, they are shifting costs to vehicles that do the most wear.
It may not appear be fair, to toll an rv at 12' H the same as a commercial 12' truck, however the difference is in licensing and usage. They count axles as the determining weight factor.
My complaint would be about electric/ hybrid vehicles who use, wear our roads and do not pay any road use taxes.
Should they ( alternative fueled vehicles) be charged a per mile tax or a registration fee upcharge commensurate to thier lack of fuel tax for the use of our roads, then possibly a fair axle / weight tariff could be charged.